The present invention relates to methods of detecting wet arc faults and more particularly, methods of detecting wet arc faults in AC power distribution applications.
A wet arc signature may be defined as a “high impedance fault” because the impedance found in wet arc faults may be comparatively very high during the arcing event. As a result, the arc produced is very small in magnitude but yet very dangerous.
The wet arc can be observed in moist environments where the salt concentration is comparatively very high. Sea water has a typical concentration of 3% to 4% of sodium chloride (NaCl). In a typical aircraft environment, moisture available in the air may get condensed and deposit on the wires as water droplets having a certain NaCl concentration. Since the aircraft goes in different forms of stress and vibrations in its life cycle, the wires, over time, rub against each other, causing these water droplets to settle at the sharp edges. Also, in some older aircraft, wires have the property that they may absorb the water droplets. As a result, the wiring strength is reduced over time.
Since the wires in aircraft are typically present in a bundle, these water droplets make their way into the bundle and may produce a continuous/discontinuous channel between any two conductors. The path which is formed is called “tracking”. Over time, the water droplets evaporate but the salt concentration still remains. Upon further water condensation, the channel is produced again. And if the channel produced is a conductive channel making a path between two wires of different electrical potentials, a “wet arc” may result. While this wet arc track may clear immediately, the salt concentration still remains and a new track may be created when the next fresh water droplets condense. Overall, the formation of wet arc faults is a slow process, but yet there is a source of energy which is always created, and over some course of time, this can create a major impact.
As can be seen, there is a need for a method for detecting wet arc faults so that damage caused by wet arc faults, over time, may be mitigated.